Plant Protection: Pests, Diseases, Weeds and Integrated Management
Plant protection questions test identification of pests, diseases and weeds, understanding of the economic threshold level (ETL) and the order of preference in integrated pest management (IPM).
IPM order
Cultural (resistant varieties, timely sowing, crop rotation, clean cultivation, balanced fertilizer - excess nitrogen invites sucking pests) → mechanical (hand picking, light and pheromone traps, bird perches) → biological (Trichogramma, Chrysoperla, Bacillus thuringiensis, NPV, neem) → chemical (last resort, need-based, at ETL).
Common examples
- Pests: stem borer (rice, sugarcane), bollworm (cotton), aphid, jassid, whitefly, termite, cutworm and locust.
- Diseases: wheat yellow rust, rice blast and bacterial blight, sugarcane red rot, potato late blight, mustard white rust, groundnut tikka.
- Weeds: Phalaris minor in wheat, Chenopodium album (bathua), Cyperus rotundus (motha) and Echinochloa (sanwa) in paddy.
Worked example
A herbicide is recommended at 500 g a.i./ha and the product is 50% WP. Product needed = 500 ÷ 0.50 = 1,000 g/ha. A 15 L knapsack sprayer applying 500 L/ha covers 15 ÷ 500 = 0.03 ha per tank, so the dose per tank = 1,000 × 0.03 = 30 g. Changing the water volume without recalculating the dose causes under- or over-dosing.
Traps that cost marks
- Calling rust a bacterial disease; rusts are fungal.
- Describing ETL as the point where the crop is destroyed - it is the pest level at which control pays.
- Spraying at full bloom, which kills pollinators; always follow the waiting period before harvest.
- Mixing weeds into a list of diseases.